This invention is directed to an antifouling fuel composition. More specifically, the present invention is directed at a fuel composition having particular applicability in minimizing and/or preventing injector fouling in gasoline engines equipped with electronically controlled multiport fuel injectors.
Over the past several years, improvements have been made in the performance of internal combustion engines. One of the most significant improvements which has been made has been the widespread use of fuel injection to improve the performance and fuel economy of internal combustion engines. While carburetor-equipped internal combustion engines admix the air and fuel for distribution through a manifold to all of the cylinders, in a fuel injected engine the fuel is injected into the manifold close to the intake valve of each cylinder for combustion. Fuel injection systems are of two basic types, mechanically controlled and electronically controlled. The early fuel injected engines were controlled mechanically, i.e., the operation of each injector was controlled by pressure. Recently, however, the use of electronically controlled fuel injection engines has become increasingly widespread. In an electronically controlled fuel injection system sensors disposed in the exhaust are employed to maintain the air to fuel ratio within narrow limits. Electronically controlled fuel injection systems offer the same performance and fuel economy benefits that would be achieved with mechanically controlled fuel injection systems and also serve to more closely regulate fuel-air mixtures to thereby enable the catalytic converter to oxidize carbon monoxide and hydrocarbons to carbon dioxide and simultaneously to reduce nitrogen oxides and thus meet emissions control legislation. Such legislation imposing as it did strict control of exhaust pollutants ultimately led to the development and widespread application of new technologies such as electronic fuel injection.
It has been found that the electronically controlled fuel injector systems have small port openings which are prone to fouling by deposits. These deposits are believed to occur, at least in part, by gasoline and oil vapor, which is present in close proximity to the injector tip, becoming baked onto the hot surfaces of the injector pintle and on the surfaces of the annulus surrounding the pintle when the engine is shut off. These deposits restrict the fuel flow to that particular cylinder. This, in turn, causes a sensor disposed in the exhaust to detect a higher than desired oxygen to fuel ratio. The sensor will attempt to correct this condition by increasing the amount of fuel injected into all of the cylinders. This, in turn, will result in a richer than desired fuel to air ratio in the exhaust. The sensor then will attempt to correct this by decreasing the amount of fuel injected into each cylinder. This cyclical adjustment of the fuel to air ratio ranging between too lean a mixture and too rich a mixture can at times result in poor operating performance of the vehicle. In addition, close tolerances in this new type of injector and concurrently higher underhood temperature also tend to enhance deposit formation resulting in poor vehicle driveability and exhaust pollutant emission levels which exceed the maximum levels set by emissions control legislation.
It has been found that conventional gasoline detergents, which have proven effective in preventing and/or eliminating carburetor deposits are not particularly effective in removing and/or preventing deposit build-up that may occur in electronically controlled fuel injection systems. Presently available methods for removing deposits from fuel injector orifices typically comprise either mechanically cleaning the injectors or the addition to the fuel of relatively large quantities of particular additives. Mechanical cleaning, which may involve either the complete removal of the injector for manual deposit removal or the use of polar solvents for flushing the deposits free, is not desired because of the relatively high cost and inconvenience. Currently available additives are not particularly desirable because product recommendations indicate they must be used at relatively high concentrations, i.e. about one to about two tons per thousand barrels of fuel.
To be useful commercially a gasoline additive for reducing and/or preventing injector port fouling must be effective at low concentration, must not significantly affect the combustion characteristics of the fuel and must not foul the catalytic converter catalyst.
The additive also should not promote excessive emulsification, and should not promote the formation of two organic phases.
Additives have been added to gasoline to improve certain properties of the fuel. U.S. Pat. No. 3,387,953 is directed at the use of organo-substituted nitrogen oxides, particularly amine oxides for rust inhibition and as anti-icing agents in gasoline. Several representative formulas for amine oxides are given including the following: ##STR1## where: R.sub.1 is C.sub.6 -C.sub.24 alkyl, aryl, cycloaliphatic, heterocyclic, substituted alkyl or substituted aryl; and R.sub.2 and R.sub.3 are the same or different and are C.sub.1 -C.sub.24 alkyl, aryl, substituted alkyl or aryl, cycloaliphatic or heterocylic. R.sub.2 and R.sub.3 preferably comprise hydroxy substituted alkyls. These compounds typically are added to gasoline in a concentration within the range of about 2.0 to about 100 pounds of amine oxide per 1,000 barrels of gasoline (ptb). Among the most preferred additives is bis(2-hydroxy ethyl) cocoamine oxide.
U.S. Pat. No. 3,594,139 is directed at a rust-inhibitor concentrate that can be blended with gasoline year-round including amine oxides having the aforementioned formula, with a particularly preferred amine oxide comprising bis(2-hydroxy ethyl) cocoamine oxide. The concentrate also comprises a liquid aromatic C.sub.7 -C.sub.10 hydrocarbon and an aliphatic monohydric or dihydric alcohol having from about 6 to about 13 carbon atoms. Preferred aromatic hydrocarbons comprise ortho, meta and mixed xylenes. Preferred aliphatic alcohols comprise C.sub.6 -C.sub.13 oxo alcohols. The examples disclose the combination of xylene, bis(2 hydroxyethyl) cocoamine oxide, and C.sub.8 oxo alcohols.
The amine oxides described above have been typically used to inhibit rust and carburetor icing. While these compounds were used commercially during the late 1960's and early 1970's, their use in the United States was discontinued as more effective additives were found. The use of these compounds had been discontinued in the United States well before the development of electronically controlled, fuel injected engines.
It has been discovered that use of amine oxides at concentrations generally higher than that which previously had been used for rust inhibition would be effective in preventing and/or reducing injector fouling in multiport fuel injected engines. However, when amine oxides are used at these higher concentrations they tend to act as emulsifiers which bring into the gasoline layer, water, sediment and impurities which may have entered the product distribution system. This prevents normal separation of the gasoline from any water or normally insoluble impurities. The admixture of these impurities is not desired with the gasoline, since this would result in excessive fuel filter fouling and in poor vehicle operation. In addition, it is believed that formation of an emulsion results in undesirable concentration of the amine oxide additive at the interface. It also has been found that the use of certain solvents to produce an additive concentrate having low cloud and pour points may form two organic layers, resulting in uneven additive distribution.
Accordingly, it would be desirable to provide an additive package for gasoline which will be effective in reducing and/or eliminating fouling without forming an emulsion with water bottoms and interfacial solids.
It also would be desirable to provide an additive package having a demulsifying agent which is effective in the presence of both neutral and basic waters.
It also would be desirable to provide an additive concentrate which has low cloud and pour points and which does not result in the formation of more than one organic layer.
Accordingly, it would be desirable to provide a gasoline additive package which is relatively inexpensive and effective at low concentrations to reduce and/or eliminate injector fouling.
It also would be desirable to provide a gasoline additive package which is non-corrosive, non-deleterious to the catalyst, and does not effect the combustion characteristics of the fuel.
It also would be desirable to provide a gasoline additive package which could be easily added to the finished gasoline at any point during the storage and/or distribution system.